Zodiac
BabylonianHellenisticCross-traditionEditorial synthesisAstronomical fact
Definition
The band of sky along the Sun's apparent yearly path (the ecliptic), divided in astrology into twelve equal 30-degree signs. The twelve-sign division originated in Babylonia and differs from the astronomical constellations.
Also called: Zodiac signs · Signs
In more depth
The division of the ecliptic into twelve equal signs was a Babylonian innovation of the first millennium BCE, later adopted and systematised by Hellenistic astrology. Signs are an idealised coordinate scheme: exactly twelve, exactly thirty degrees each.[1][2]
Astronomical constellations are a different thing: the modern sky is divided into 88 official constellations of unequal size, and the ecliptic actually passes through more than twelve of them. Because of Earth's axial precession, the signs and the like-named constellations have also drifted apart over the centuries, which is why tropical and sidereal zodiacs exist as distinct conventions.[3][4]
References
Numbered citations in the text link to the records below; each record links to the full source registry.
- Francesca Rochberg. The Heavenly Writing: Divination, Horoscopy, and Astronomy in Mesopotamian Culture. Cambridge University Press. 2004. Historical scholarship View source record
- Nicholas Campion. A History of Western Astrology, Volume I: The Ancient and Classical Worlds. Continuum. 2009. Historical scholarship View source record
- International Astronomical Union. The Constellations (official list of the 88 IAU constellations). current (living reference page). Astronomical fact View source record
- NASA Science. Milankovitch (Orbital) Cycles and Their Role in Earth's Climate. 2020 (last updated 2024). Astronomical fact View source record